The objectives of the project remain to study the uniqueness of cartilage, a tissue resistant to both capillary and tumor invasion. We have isolated from hyaline cartilage an anti-invasion factor (AIF) which contains a spectrum of low molecular weight cationic proteins that act as protease inhibitors. Potentially invasive cells such as tumor cells (human osteosarcoma or metastatic breast carcinoma cells) or endothelial cells, but not fibroblasts and smooth muscle cells, are inhibited in their proliferation in culture by AIF. The proposed research intends to biochemically separate and identify the active components of this cartilage derived anti-invasion factor.